The present invention relates to a digital signal recording apparatus and a recording medium for recording digital compressed picture information on magnetic tape, and specifically the structure of the recording apparatus that suitably records picture data for a trick-play separately from recording data for a normal replay and the recording medium on which data is suitably recorded.
Digital broadcasting such as, typically, digital satellite broadcasting is spreading widely. Video tape recorders (VTRs) to record and replay digital broadcasts with digital signals being as is are proposed.
In digital broadcasting, picture information is compressed and transmitted through the use of a digital picture compression technique for effective use of radio wave bands. A typical digital picture compression technique in use is a Moving Picture Expert Group (MPEG) method. Digital picture compression reduces data quantity by making good use of mutual connections between successive picture data frames.
VTRs for recording digital compressed pictures have difficulties with trick-play operations such as fast forward and rewind. This is because digital picture compression uses mutual connections between frames and reproducing pictures from part of the picture signals from magnetic tape is attempted when a trick-play is requested, but original pictures cannot be restored from only the part of the signals.
To resolve this problem, VTR systems have been proposed that record in advance only intra-frame coded pictures on magnetic tape in position that a rotary magnetic head passes as it scans in trick-play mode without using mutual connections between frames. (These systems are described in Japanese Patent Prepublication Nos. Hei8-46913 and Hei8-98140.) These systems make it possible to reproduce intra-frame coded picture data from magnetic tape and restore pictures in trick-play mode.
Another VTR system compresses data at a higher compression rate and records the compressed data in position on magnetic tape in a separate process from the process of a normal replay of digital compressed pictures, which is described in Japanese Patent Prepublication No. Hei5-276491. This system, which converts input picture signals into digital compressed signals to record picture data, uses a separate higher-rate compression circuit for executing data compression at a higher rate to generate trick-play data, separately from the normal compression process, and disposes the data in place on magnetic tape. In this way, pictures are properly reproduced even during a trick-play.
Furthermore, recording and replay equipment that records picture data while removing all or part of the fixed patterns and redundant data of picture data is described in Japanese Patent Prepublication No. Hei5-125966. This recording and replay equipment extracts intra-frame coded data from input picture information and deletes headers, high-band coefficients of AC components, fixed bit patterns, etc. from the data when recording the data. The device reconstructs MPEG bit streams by inserting the deleted data when executing a replay.